I got this from yahoo:
A social network. The Greenwich study also found that having friends was far more important to retirement bliss than having kids. Those who have strong social networks are 30 percent happier with their lives than those without a strong network of friends. Having kids or grandkids had no impact on a retiree’s level of contentment.
The article also mentioned that if your income is close to what you had before retirement you are more likely to be happy.
If anything kids and especially granfkids just add a lot of drama to peoples lives but little satisfaction, now dogs and cats on the other hand I bet lead to much more satisfaction in later years.