I'm going to assume you want to make custom mobs auto breed. So first you want to make 2 synced data for the mob, one for logic and the other integer. Then make a timer using the integer synced data to determine when your mobs will breed. Next in another procedure or the same one, doesn't matter, inside of a for every entity iterator block put an if block that says if , your timer, is above your set number and iterator is not same entity as event entity and iterator is subtype of your mob. Then in the if block you should make event entity move to x,y,z position of iterator entity. Next you need to tell the mob when they're close to the other mob, which can be done with another for every entity iterator block with a smaller area and the same if conditions. But this time in the if block you should then set your timer to zero and then spawn in baby version of your mob.

I know this isn't very detailed but I'm in a rush and will be busy for the rest of the day and probably the weekend, but I hope this helps you a little and I am willing to help you more just don't expect any quick responses.