Awarding Happiness Points

I started a new family today, but instead of starting with one young adult, I started with two adults, one teen and one child. But, it occurred to me that the adults and the teen, at least, should have earned happiness points along the way. It makes no sense to start them all off at none. So, the question is, how many points per life stage sounds reasonable? I was thinking maybe 5,000? I don't know. What are your thoughts on it?