How do things change with your friends who don't have children when you do?
Depending on your age and the respective ages of your children and your friends, things quite often change once you enter into the realm of parenthood.
When you are a young parent (in your late teens to late twenties,) you often have friends that are still single and unattached. Once parental bliss becomes an ongoing part of your life, these friends may become either "fairweather" friends that are completely intimidated by the sound of a crying child or smell of a poopy diaper. These are the first type of friends that you lose. Or you may have the type of friends that consider it an honor to babysit for you whenever they can. These friends thrive on this vicarious experience without having to deal with the responsibilities 24/7.
When you are in your 30s - 40s, all of your friends are quite often married with children, divorced with children, or even single with children. Your friends tend to include individuals with kids near the same age as yours, sharing in the same interests. You often build a brand new circle of friends based on these commonalities. You tend to spend a lot less time with friends that do not have children.
But become a single parent, and it's a whole new ball game. Your married friends with children often side with either you or your ex-spouse and this changes the dynamics of those friendships for all concerned. Again, you often build new friendships with other single parents and may retain some true-blue friends that can accept you and love you in any circumstance. If you have a split custody situation, you may find it easy to cultivate new friendships with individuals without children during the time your children are with the other parent. It can be a best of both worlds situation for everyone concerned.