Letter for accommodation issue

[call2bala]

Hello experts

This forum is great platform for all. I could not find a similar situation of mine in this forum so I am writing this to ask few questions.

I gave my friends family a letter of accommodation in my 4 bed property and they want to migrate from Australia. In the letter i stated that there won't be any rent for their stay while looking for their own accommodation (only provide accommodation for their 2 adult+1 baby family but they show their finances separately for British dependent visa) . My friend is applying based on British Ancestral passport dependent root and i think it will be under process just from August /September.

Just realised I am inviting my parents through FAMILY VISITOR VISA in November and I am sponsoring their trip, stay in my own 4 bed property and everything for their entire stay in UK

Question:
1. based on the letter i gave to my friends family, CAN HO reject my parents VISITOR VISA?
2. There will be a gap of 1 to 1.5 months between My friend's family visa processing as British dependent and my parents visa application date. Is that so close and critical for my parents VISITOR visa decision based on I am inviting 2 people with in a span of 1 or 2 months?

Could you please share your thoughts and experience .

Thanks