It's natural to spend most of your free time with your spouse,mate, or whomever you fall in love. After all you are considering building a future (together). Eventually your lover becomes your "best friend" in the best of scenarios. However it doesn't mean you "avoid" your best friend or cut them out of your life. Your (family) meaning your spouse and children are suppose to be your #1 priority.
Any mature friend not only gets that but also would be the same way with their own (love, spouse, family). There should not be a "competition" between spending time with the one you're in love with and spending time with a friend. Most people are able to carve out time for their friends even when they are in relationships. Others invite the friend and their significant other to gatherings. A great friend is happy when their friend finds love. It's proof that it can happen. He or She has to accept they are now on different paths until they find a love of their own. "Birds of a feather flock together". Most couples spend time with other couples. Most singles would rather hang out with other singles than couples. It's natural and nothing "personal". It's to be expected!