Advice on introducing young degus?

[Mel]

I started with 3 male degus who are roughly 2 months old, ive had them for about 2 weeks now so they're all settled in and have established their territory.
but recently my friend's degu had babies and because hers are all girls she couldn't keep the boys as well so I had them, so I got 2 new boys which are a bit over 5 weeks old now.

The cage they have is a double floor cage so I put the young ones on the top floor and the oldest on the bottom floor and raised the ladder and blocked the hole so they can see each other and smell each other but can't get to each other.

They've been able to see each other for about 4-5 days smelling each other through the bars and I was advised to introduce them and just see what happens and if there's any mounting to ignore it... only I couldn't ignore it, the young degus were being chased all around the cage by the big boys being mounted and squeaking quite loudly, and although there was no fighting I just felt a bit bad about the big boys pestering them so I separated them again.


What's the best way to get them to be friends? I know there's no guarantee they'll ever be friends but I'd like to give it a try first so they can share a cage rather then keep the cage split.

The big boys beat their tails when they're smelling the young ones through the bars, and the babies seem pretty keen when they can't actually get to each other but once their in the same space with each other it turns into the young ones running away and squeaking and the big boys pestering them.