Can I use 'he' in this sentence?
John and Emma live in London. He is single.
OR
John and Emma live in London. John is single.
For me it sounds very inaccurate to refer to John by using subject pronoun he. I had a discussion about this with my spanish friend and I was very doubtful if it's allowed to use 'he' in that sentence. I tried to find a grammar rule which would prove that, but I didn't find anything. So, what's the truth?How about these sentences?
John and Emma live in London. HE is single and SHE is married. IMO the latter sentence wouldn't be very often used in spoken language. Atleast I would use names instead of subject pronouns in both of the cases.

Question

Can I use 'he' in this sentence?
John and Emma live in London. He is single.
OR
John and Emma live in London. John is single.
For me it sounds very inaccurate to refer to John by using subject pronoun he. I had a discussion about this with my spanish friend and I was very doubtful if it's allowed to use 'he' in that sentence. I tried to find a grammar rule which would prove that, but I didn't find anything. So, what's the truth?How about these sentences?
John and Emma live in London. HE is single and SHE is married. IMO the latter sentence wouldn't be very often used in spoken language. Atleast I would use names instead of subject pronouns in both of the cases.

Answer

Yes, you can use HE, as it is obvious you are referring to John and not Emma.

Answer

No it's not inaccurate. John is a male name. It's not a unisex name so it's clear you are referring to him.

Answer

Both "John and Emma live in London. He is single." and "John and Emma live in London. HE is single and SHE is married." are correct and natural. It would get confusing if one or both of the names could refer to both men and women, but since that's not the case here repeating the names would be redundant.

Answer

Hi Saku !
Here you introducing John and Emma so it would be confusing that who is single , John or Emma ?  But it can be guessed by gender. It is better, you use name instead of pronoun "he"