Y'know, sometimes when autism's involved, people have to be a little creative about their expressions of affection. I remember one mother and son, with the son being really tactile-defensive and hating hugs, who used to touch their fingers together instead of hugging, to say I love you. I don't mean you ought to do exactly that, unless you happen to want to; just that you're family and you'll find a way, even if it does happen to be odd.