Texas became independent of Mexico and was a republic for ten years. Newfoundland was a British colony before being given self-rule as an independent Dominion (just like Canada). Both countries voluntarily relinquished independence and requested annexation and admission to a larger country. Neither were once part of the United States or Canada respectively.Both Texas & Newfoundland are cases of offspring reuniting with the parent state.
In both cases, it was the smaller countries requesting annexation to the larger.