Firstly, I'm not looking for an organism that gives birth to two separate species (like a human that gave birth to a human baby and a puppy) as I'm fairly sure that is impossible (though feel free to correct me if there is any example of that).
What I'm thinking is a symbiotic pairing that utilise the same egg (or seed, I'm happy for one half of the pairing to be a plant) to give birth to their young.
Obviously for an animal it would be easier if it was egg laying than mammalian with live births.
What I imagine is species one lays an egg or produces a seed and the second species either implants their own egg / seed into it or somehow absorbs the first egg / seed and grows it's own around it. I imagine the issue would be the first egg being damaged by the process, but I'm hoping it might still be possible.
So the question is, is something like that possible? Is there any example of it happening in real life?