Go to the lobby. Select the bell three times, then the phone once and repeat the process. If done correctly, heads will be large. They will return to normal after restarting the game.
A couple will have babies if you get a letter back with an "A+" grade. The couple can be gay or straight, and the amount of children can vary but is usually two. The difficulty is finding a client and a candidate that are a good match. An "A+" grade requires a very good match where they have things in common or can deal with everything. Some luck may be required. Consider doing the following things to increase your chances.
When you get new candidates, have a client test them to reveal some personality traits. Use less picky clients to date and get a feel for people for a date or two. You can do this as long as the client does not reject them outright and you did not make too bad of a mistake to get them dumped. That candidate may not end up being a good match for your client, but you you may get Mr. or Ms. Perfect later for them.
Go to the "Friends" screen and keep selecting your own avatar and your friends' avatars. You will get a money bonus and a reputation bonus for doing this.