Nakapunta ka na ba *kina John (or sa bahay *nina John)? Sabi niya, kapag pumunta (or nagbakasyon or napasyal) ako sa Pilipinas, pwede daw akong mag-stay (or tumuloy) sa *kanila. If he lives alone, you can use "kay/ni/kaniya." If he lives with other people, even if he is the owner, use the plural version (this is more of a cultural thing rather than a grammatical thing).

Have you been to John’s house? John told me that if I come to the Philippines I can stay at his house. --- Nakapunta ka na ba sa bahay ni John? Sabi ni John sa akin na kapag pumunta ako sa Pilipinas pwede akong tumuloy sa bahay nya. (translated based on its original sentence) Nakapunta ka na ba kila John? Sabi ni John sa'kin na 'pag pumunta ako sa Pinas pwede akong tumuloy sa kanila. (informal and more natural Tagalog expression) It is more natural to use contracted words to express your thoughts. sa akin - sa'kin kapag - 'pag Pilipinas - Pinas John's house - it's more natural to say "kila" Have you been to John's? Nakapunta ka na ba kila John? at his house - it's more natural to say "kanila" I can stay at his house. pwede akong tumuloy sa kanila.