PLEASE HELP! Prep Work for Parents B1/B2 Tourist Visa after 6 Denials Rejections?

Hello, Sorry for the long post but here is entire history.

Jan 2009 - I, came here on F1 visa Jan 2009.

Dec 2010 - I went back to India only once for 3 weeks.

May 2011 - I graduated and we tried for my parents tourist visa for first time but we missed to have graduate invitation and my mom dad couldn’t answer about my employer so was denied.

May 2011 - Nov 2019 - I maintained my F1 visa through some small university but never went back to India as I didn’t have stamping and own a small business.

During these years my parents reapplied multiple times but each time they were rejected asking where is your son? Why doesn’t he come to India? We don’t remember the reasons they were denied. My Parents have visited 18 different countries but denied in US. Last visa rejection was may be 2018.

2021 - I got my Green card (2yr) through spouse (non Indian US citizen) I went back to India in Oct 2021 (solo) after 11 years. My spouse has never visited India. My sister, who is married and visits me every year was also there for our wedding.

2022 - We applied for their Canada visa too and that got denied as well.

2023 - I have applied for my 10 yr GC and wait time is 2.5 years.

Now we have reapplied for Tourist visa appointment for my parents 7th time. My dad mom both are 60+ and only have real estate business so yes minor binding in GJ, India. Ofc they are coming to meet my spouse.

We are nervous and would like to know what all preparation to do?

E.g. may be show as they are planning a trip with my sister n brother in law? Or anything related to my spouse? Finances anything? How to prove that their stay in US is temp and not permanent? Also, we are able to prepone visa app from Sep 2024 to may be Dec 2023. Should we prepone or keep it the same? Anyone been through something similar or can guide? Thank you very much for your help in advance.