Having woman problems. please help!?

I have a close female friend of mine, her and her cousin always hang out, my female friend has a boyfriend but her cousin is single, she is extremely pretty. I don't want to be straight forward creeper and just ask for her cousins number, is there anyone who can give me advice to possible get her cousins number respectfully without my female friend minding, shes a pretty chill person so i'm sure things will conclude positively, i just need some advice on this, thank you!!