Suppose but his brother married very quickly and romantically. One of the many things I dislike about Federer is that he only married his girlfriend of ten years when she was having a baby. I think Andy will be lucky if a lovely girl like Kim is willing to hang about for years without commitment from him. If he loves her he should want to marry her - old fashioned I know but still true.
Everyone is different though-just because Andy hasn't married Kim yet,doesn't mean he doesn't love her or isn't committed to her,and we don't know that he doesn't want to marry her.They're both young,and he lived through what was,by all accounts,not the friendliest divorce when he was a kid.We know that left an impact on him,because he's said so!Doesn't mean he won't marry,just that he might not want to do it as fast as others.
Plus,he might actually just want to wait until they have time to do it and enjoy themselves-he has a very,very full schedule during the year,and he trains during off season too.I seem to remember reading in an interview with Jamie that he actually didn't get to take his wife on a honeymoon,because a few days after the wedding,he was playing tennis in some other country!And the scale Jamie plays on is less that Andy's,so presumably it would be just as difficult for Andy to carve out a block of time,if not more so.