I agree with Gabby's thought. I repeat birth charts too. Two major love relationships in my life are VERY similar, only born two weeks apart. I have a thread about it. They are both cancers, with the same mars, jupiter, lunar nodes, and outer planets. Thankfully their ASC and thus houses are different. Like you have found, the relationships are also very different.
I also have repeated Leo 15. I had a very significant best friend relationship that somewhat blew up and ended, and then later I dated a man with the same birthday, but different year. That was fleeting, but it still struck me as odd that it was the same sun degree for them both. Their venus' were very close too, and though their mars were very different, both of them had air mars that closely aspected my pluto. Weird. But I have found I am very drawn to pluto interactions.
For me, I think all these people are hitting significant spots in my chart. For example, Leo 13 is my venus/jupiter midpoint. I also have arabic part of marriage at Leo 16, and cupido at Leo 14. 17 Leo is sun/venus. 12 Leo is venus/vertex and saturn/sun, as well as asteroid angel. So thats a pretty good range of sensitive points for me. And while I natally have nothing in the teens in leo, I am really drawn to people that hit these points.
I configured as many midpoints as possible and found that my synastries often hit these points, usually with conjunctions and then also with squares. Virgo 14 is my mars/venus midpoint, and that usually gets picked up. I see a lot of gemini 14 hitting my synastry- and in my chart I have NOTHING on gem 14. But then again I do have neptune at sag 15. However, looking at these gave me some insight.
I found scorpio 5 was getting hit a lot, and though its not a major midpoint, it was my neptune mars midpoint. Researching this showed me it reflects my spiritual growth. Spiritual growth is a big lesson for me this life time, both as seen in my north node as well as something I feel very strongly compelled to do. So I am not surprised that it is an attraction point for me in the synastry charts.
So my point is that check for midpoints. It may be karma, it may be that these people bring something to the table that you need for your growth and development.