Can Goten & Trunks use SSJ3?

[SSJ2]

After their training in the RoSaT, do you think they are capable of using SSJ3? Goku is almost pissed by how easily Gotenks managed to use/acquire the form. It doesn’t make sense to me that the kids would forget how to transform after defusing. What do you think?

 

[PorchMaster]

I don't think they can. Achieving SSJ2 and SSJ3 so fast appears to be an effect of the power boost of the fusion, plus while Vegetto and Gogeta can use Shunkan Idou Vegeta can't. For what it's worth Vegeta also failed to learn how to use CSSJB from being fused with Goku in the Super manga.

 

[Pyro]

Well, just knowing about something doesn't mean you can easily do it. Vegeta knew about Metamoran Fusion but still had trouble performing it. The same principle would apply to the kids and Super Saiyan 3. Just because Gotenks could do it doesn't mean the kids individually would be able to at the time.