My parents did both as well, although they both gradually got out of horses, it was more that their interest waned and other passions took it's place. My dad bought 2 TWH weaning when I was 3 months old and their brother the next year. We had them until their deaths at 23, 27, and 30. Horses don't mind "sitting" in the pasture eating and being horses, they don't mind just being groomed, or just giving pony rides either. There is something nice to be said about watching your (a) child learn to ride on your horse or seeing your horse love on your (a) child.
I'm not a mother and I don't know if I ever will be, I love kids, and am fairly certain I would be a very good mother, but I also love my animals and am completely content if I never have children. I also have some lovely godchildren (6 at last count) and at least one, probably three or four who would come to me if anything happened to their parents. Although, like I said, I'll probably end up fostering and/or adopting someday so I'll end up having kids no matter what happens in life. If I marry I probably would not marry someone who had a burning crazy desire to have his own biological children, I'm getting older and do not personally agree with fertility treatments and I wouldn't want to take something like that away from someone else.
Boy that was just a whole ball of ramble, wasn't it? Please excuse, I'm sick and just woke up from nap.