while megatron is a natural carrier and has carried many times in his life, starscream isn't, has never carried and it's not something he can naturally do, even though he wants to do it. in a lot of my aus, esp my tfp aus, the two of them run into a lot of trouble when they get together regarding starscream and carrying. it's weird to him because seekers don't ever carry, they are great sires- he's carried with seekers before during the war and even a bit after. And like all seekers, megatron just realizes starscream can't carry naturally, but it's still a desire of his and while megatron has only ever carried, he doesn't mind siring for starscream just because of how close they are. or at least, attempting to. starscream has to get a lot of procedures done to do it, many failed and unsuccessful. It's a first for siring for megatron too but he wants to do it with starscream.
the point of this little fic and running au of mine is that, while starscream has so many difficulties carrying, megatron is there for him. with every failed procedure and how depressed starscream is, he tells starscream about his own experiences to make him feel better. starscream eventually asks about it, how it feels, what it's like, emergence, etc. and when things don't work for starscream the first few times, megatron is always there to encourage him, and he convinces starscream not to give up.
eventually, things do work out and starscream is able to carry multiple times, but starscream enjoys hearing a lot about megatron's experiences. Starscream also listens carefully to what Megatron says about his past. He had many relationships where he was happy with his partners, and he carried and he and those sparklings are in close contact, but there are some more somber stories, where Megatron's sparklings were taken away from him when he was in the mines, where he was only used as property to produce more miners and he's lost those sparklings. Or where shortly after he had his sparklings, his partners took them from him no trusting him to be a good carrier (during the war)
Obviously, Starscream takes it upon himself to track down megatron's missing children, the ones he's lost contact with, the ones he doesn't know, etc. This isn't something unique to my tfp stories, where this au started. In most of my fics, Starscream goes looking for all the children taken from Megatron while he was carrying.
But the gist of this is that, Starscream has a lot of issues and difficulties with carrying because seekers aren't built for it, but megatron is always there to help him and make him feel like less of a failure and also help him after his emergances, because it's incredibly difficult for starscream.