I have a 7 year age gap.
Its can be very difficult. Trying to find something that entertained a 2 year old and 9 year old made days and trips out difficult. Trying to find a movie that suited both at the cinema or a movie night in. We needed to make sure the older wasnt impacted by not being able to do certain things, because of her younger brother. In these cases just one of us went with her and the other with the younger one.
They are 15 and 8 now and they get on to a certain degree. I would say similar relationship to me and my brother and we were 3 years apart.
It was difficult. But then having 2 close together is difficult for different reasons. So I dont believe that one is better than the other. Neither ensures a good relationship or ensures a poor one. They are hard in different ways.
That said, its quote unusual to not live together whole raising a child. I would see how that goes first, which it sounds like you are
Also, I wont have anymore. I have no intention of doing the baby stage again. No one could convince me other wise.
Hundred of people can tell you they changed their mind or their partner did. Or that they didnt. It's not going to determine wether he will or not.
This isnt a situation you can compromise on. And every situation where the second has been a 'surprise' when one doesnt want any more, ends up in a relationship breakdown in soectatulat fashion.