What if Robin's father had ignored his son's tantrum and married Wills mother anyway. Robin left on the crusades when he was 20-23 and Will was 5-8 (going by the age difference between the actors, and what age you want them to be). Robin had been in the crusades for 10 years (because I haven't watched the film recently and can't remember)
Robin had been furious when his father had refused to give in to his demands and had married the Peasent woman anyway. He was even less impressed, when eight months later he was forced to listen to the squalling wails of a newborn child. He refused to have meals with his father and the Woman, refused to speak to them, and refused to even see them. His father was being surprisingly leiniant of his continued tantrum, usually he would have been dragged in for a long talk about how to act as a noble. It was all the Woman's fault, and the damned screeching child.
The silence continued until the baby was nearing three months, when the Woman fell ill, and his father became frantic for her health. It was a sickness similar to that which had stolen Robins mother from him. Robin, through the gossip of the staff, had learned that the Woman had being caring for the child herself, and now that she was ill the task was now the staffs. The child however, refused to feed.
Robin, through morbid curosity had decided to visit the childs room, and witnessed one of the women trying to feed the child cows milk from a bottle. He watched as her frustration grew to the point that she set the child and the bottle down and left the room, muttering darkly about needing a wetnurse, and how she was far too old to be looking after children.
Robin stepped into the room after she had left and for the first time, looked into the wicker crib that held his fathers newest child. A boy, he could only assume, by the blues he was dresed in. The baby looked at him, eyes bright blue, but beginning to darken around the edges. The baby reached up a tiny hand, and before he could stop himself, Robin had reached in a finger, and once that small hand had wrapped around that single digit, he was lost, and no amount of reminding himself of his hatred for the Woman and her offspring could prevent it.
It took him a long few miniutes to work ot how to lift his brother safely, and longer still to coax him into drinking from the bottle. And as the child finally began to drink.
He apologised to his father the next day, and to his new wife when she got well, and for everyday in between, he coaxed his brother into drinking his milk, and fell a little bit in love with him every time.
"But why can't I come?" Will whinned.
Robin rolled his eyes in exasperation. They had had this conversation many times over the last few months, since he had announced that he would be joining the crusades. His father had not forgiven him yet, but had not stood in his way. Anna, his fathers wife, had said nothing, but her silence spoke of her saddness that he would leave them. His brother however, had done nothing but beg to come along, he demanded, pleaded, argued, yelled in fits of temper, and refused to believe that when Robin said "No." it actually meant, for a change, "No."
Robin only had himself to blame of course, he had spoiled his brother to ridiculous lengths from he was three months old, had refused him nothing, had taught him to hunt, to fish, to ride, all while their father looked on with an indulgent smile. Not that Will was a bad child. In fact he was quite humble in his wants, and would return whatever he had recieved a thousand fold in his love.
"It's too dangerous Will." he said.
"But what will you do without me?" Will asked him.
Robin sighed, knowing this to be a prelude for a tearful "You'll forget about me". He turned and knelt in front of his brother and put his hands on his shoulders. "Will, I need you to listen to me carefully, can you do that?" Will nodded unhappily. "Will, I need to go away, to fight in the crusades. It will be long, and dangerous, and it is not place for a little boy, no matter how brave or strong he is. And besides, you have the more important job right here at home."
"What?" Will asked petulantly.
Robin smiled. "You must look after your mother and our father. Father's getting older, and he will need your help to defend the castle should the need ever arise."
Will seemed to consider this, as he had numerous times before, and finally nodded, slowly and gravely and looked Robin dead in the eye, and said, far more seriously that ever before. "And you will not forget me?"
Robin could see the tears his brother held back, and felt his own sadness well up, and he grabbed his brother and pulled him close. "I could never forget you."
When they parted they were both crying, and the sadness only deepened when Robin climbed onto his horse and began the long journey to join the army, and the crusades. "I will be back." he promised in a whisper. And he would, for he was determined to see Will grown. But he knew he must join the crusades, so that the world would be safe for Will to grow up in.
Robin rose from the water, and stood dripping, staring dumbly at the rope that had tripped him, and the people who were beginning to emerge from the surrounding forest.
"There was a Rich man from Nottingham, who tried to cross the river, what a dope, he tripped on a rope, now look at him shiver!" someone singsonged. "Beg for mercy Rich man!"
Robin looked from face to face until he found the singer, who was grinning at him. It took no more than a moment to recognise him, and Robin was wading his way across, ignoring the way the other woodsmen tensed as he approached, fingering their staves and bows.
The singer's grin widened, and in seconds the two brothers were laughing and hugging, ending up in the river once again. Later, once the reunion was ended, they talked about their father, and what had happened. Robin soothed his brothers guilt over his fathers death, and soon after the fight against Nottingham began.