No.

In Jainism, there is no strict rule that two souls are forbidden from meeting in a heavenly realm after human birth. Whether they meet again depends on their own karma, rebirth, and the specific heavenly realm in which they are born.

Also, watching 18+ content is a form of sexual attachment and mental defilement, so from the strict Jain view it can bind bad karma and affect future birth. But it does not create a divine “forbidden” rule that prevents two souls from meeting.

So the strictest Jain answer is:

No, Jainism does not forbid it as a fixed rule.