My DS is 2.9 and currently an only child. This isn't likely to change any time soon, if ever. He goes to various groups (he'll start going to preschool when he's 3), and we also spend a lot of time with another family who have a 2yo and a 4yo, and they are very close.
DH and I dote on DS, and while I like the fact that he gets a lot of attention from us, I don't want him to become a spoilt brat. I know that I am more patient / indulgent with his misbehaviour and idiosyncracies when it's just him, compared with when all three kids are together.
Any tips from parents of onlies on how to keep them well-adjusted - things to do or bad habits not to fall into?