The real fans of Star Wars are talking about Han Solo having twins, a boy and a girl. Is there a canon answer to that?
The Solo twins were regular character in the Star Wars Expanded Universe novels, and are quite popular among many fans of the EU, but are no longer canon; they were relegated to the non-canon Legends continuity with the rest of the EU following Disney's takeover of Lucasfilm.
In the current canon, Han and Leia only have one known child, revealed in The Force Awakens:
Kylo Ren, whose birth name is Ben
Whether Disney will borrow any elements from Jacen and Jaina's adventures remains to be seen; there's already at least one similarity:
In the Legacy of the Force novels, published between 2006 and 2008, Jacen Solo fell to the Dark Side and became Darth Caedus. One of his more unsettling acts was killing his younger brother, Anakin Solo.
The similarities to The Force Awakens should be obvious.