unfortunately i have seen plenty of folks who have married within family and have had massive fights/headaches/sourness/divorces...
your partner truly is a googly, you can make a good guess that how the person will be... but you never know how they will turn out to be...
I think there is no perfect/guaranteed way of finding a top notch partner... its all about luck, ur partner can turn out to be the devil or an angel... however what you can do to decrease the chances of them being evil or increase the chances of them being an angel is by...
1. Do not pick a partner on I WILL CHANGE HIM/HER, this fails massively... and a lot of desi ppl make this very mistake... you cannot change a person for who they are... for example and putting it very bluntly, you can dress up a donkey real nice, but it will remain a donkey... so think hard about their personality, attributes, attitude, traits... make sure they are on par with ur education, work, life style, habbits etc...
2. We all spend our lives 20+ years in a particular way... and somewhere in the back of our heads prefer it to be that way going forward... however, once married you have to realize, you will have to give up somethings, and you will have to adopt a few things, you can't stand out there like a stone and not accept any change, or fights/break ups will occur... the other person wants their space and activities or life style to be carried out a bit too...
3. Respect, Trust, and Honesty + Give a little bit of personal space despite being married, we desi folks are like leeches, and just cling on and want to know every damn bit of detail... take a chill pill, let them be themselves or by themselves for a bit once a while... ignore little stuff...
4. Talk to your partner and be open about things... communicate openly about how and where do you expect to be in your life etc... this helps out believe it or not... we folks dont do this at all... my wife for example at first was like what the hell are you on about... but then she got the idea, and it helped a bit...
5. Do not involve family members into your married life... yes have their blessings and thoughts here or there, but make your decisions with your spouse in mind first...
6. I think we assume (or family pressures/jokes/banters) that once we are married there has to be a baby... NO... just coz you are married it does not mean have a baby right away... discuss with your partner... wouldnt you want to go out for movies/vacation/work/education/etc etc before you go the baby route... dont have a baby for the sake of having a baby, be ready to raise them first... often a lot of marriages break coz couple wasnt really ready to raise a baby...
once you keep these things in mind... you could avoid lot of big headaches...
i told my wife, i am already very happy in my life as it is... and with you coming in to it, i dont want to make a soap opera out of it, i want to be happier... and vice versa... I THINK SHE GOT IT
(here is hoping lol)