How do you say have a sister in welsh?

There are a few ways to say "have a sister" in Welsh, depending on the context and formality:

Formal:

* Mae gen i chwaer. (This is the most literal translation and sounds quite formal)

Informal:

* Mae chwaer gen i. (This is a slightly more informal way of saying it)

* Rwy'n cael chwaer. (This means "I have a sister" but is less common than the other options)

Other options:

* Fy chwaer. (This means "My sister" and could be used in a sentence like "Mae fy chwaer yn byw yn Llundain." - My sister lives in London.)

You can choose the best option based on the situation and your level of formality.