Obviously the model of get married at age 20, stay married for 70 years, then both spouses drop dead was not one in the Gemara; if nothing else, enough people died young that remarriages were common. Kesubos, for example, talks about whether a wife has to nurse the babies that her husband had from a previous marriage.
Similarly there's the story of a rabbi who keeps a skull in a special box, and his wife thinks it belongs to his deceased ex and he hasn't gotten over her!
But does the Gemara tell stories of the relations between siblings in a blended marriage? (Bava Brady, so to speak?) None are coming to mind at the moment. Though I think in general the Gemara doesn't deal much how kids interact with each other.