I think Itachi and Shisui were up to adopt a kid. There was some serious bromance going on there but society back then needed a change, to be more open, so they trained on the top of a mountain, broke back mountain, while making plans of a day where their love would be accepted by the Uchiha clan.
I will just leave this here..
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OT:
We don't know. If his thing was working, why not ? It is
plotholeable.. guess we have to wait.