A big no from me too!
We also kept them together when we were children - it was just what everyone did and the Internet didn't exist so information sharing was far more sparse. Our first pair, Harold and Smokey, actually lived together very happily. So, when they died, we did the same thing again. Big mistake! It became very apparent that Charlie was really bullying Gizmo - he'd chase her and try to mount her. We immediately took her out and ended up getting her 3 guinea friends to live with - she was so much happier. I've never kept them together since then.
I think that people still do it as they've done it before and it's been fine, but my experience shows that there is no guarantee that the next time isn't going to end in a catastrophe. I really see no reason or excuse for it these days - it takes about 5 minutes to search on google and find out that it really isn't safe. Why not just find them friends of their own species?