Hi J.! I am a SAHM to 3 kids who are rather spaced apart. And I am the younger of 2..my brother and I are 6 1/2 years apart. As a sibling, it really hasn't mattered to me that my brother is so much older than me. We have nothing in common anyway...I don't know that the age difference really mattered. We just are very different. I still love him because he is my brother...I just don't always like him. :-)
As a mom....my kids are 10, 7, and 2. After my first, I knew I still wanted at least one more...but I had those same feelings about the diaper bag. That's why I decided when the first was 2 that if I was going to do it, I needed to do it then or it would NEVER happen. As for the third kid...my husband and I had decided together we were done. Two was enough! We had 2 girls and would have liked a boy but they were so good and independent...we didn't want to start over. Then, almost 4 years ago, my husband was diagnosed with a faulty heart valve and had to have major open heart surgery. After his recovery (and the birth of our only nephew), we decided that life was short and we both really wanted that boy so we would try again. We were blessed with our boy. However, we did have to start all over....which I HATED!!! But it ended in time and now he is big enough that we can take him do do the fun stuff too. I don't regret for one minute deciding to "start all over". My girls get along better with their little brother than they do with each other.
Point of my story...you can't KNOW whether or not your kids are going to get along with each other based on their age difference. There are so many factors that come into play...it is up to God whether or not they will like each other. But they will love each other just because they are family.
If you have any thoughts that you MIGHT want to have another kid...then you DO. Take it from someone who is DONE and has no thoughts whatsoever about having another kid....when you are truly done...YOU KNOW! Before my husbands surgery we said we were done. But we both still yearned for our boy. So we wouldn't take any steps to guarantee we couldn't have any more.
That doesn't mean that having another now is right for you. But don't seal a door that you may need to go through again.
Best of luck in making your decision. Just know that it has to be right for you and your husband. Not anyone else and not just one of you. But I doubt you will ever regret "starting all over".
T.