its baba ajit singh ji nathmalpurwale, they did sachkhand gaman in late 70's i think, not sure tho.
and they are differnt from baba ajit singh ji hansali.
giani ji mentions both in katha.
baba ajit singh ji nathmalpurwale were a "gurmukh brahmgiani", which is the 7th stage of brahmgian, ("satvi bhoomika de brahmgiani" is how they say it in punjabi)
this highest stage possible for manukha dehi, as the 8th stage is where maharaj is. but manukh's cant reach 8th stage while living in manukha dehi.
baba ji used to always call people as "dheen diyaal ji" or "rab ji"
this one time sant gurbachan singh ji, along with the jatha singhs, went to go meet baba ji, and baba ji was feeding or doing ishnaan i think, of the dangars (cow/buffalo), and the sevadaar told them that sant ji was here to meet them, and baba ji put down the sangal of the dangar, and grabbed a basket that had parshade in it and started giving them to the jatha. baba ji didnt wash their hands tho, they first gave 2 parshade to sant gurbachan singh ji, and sant ji knew that baba ji was pooran brahmgiani, so they didnt say anything, and just ate the parshade. but when baba ji went to give parshade to the jatha singhs, the singhs were like, "nahi ji, this is not the right maryada" and stuff like that. cuz the singhs were always tought about keeping strict sucham by sant gurbachan singh ji. but then sant ji told them to not do shanka and just take the parshade. so then each singh was given 2 parshade. and after eating the parshade, the singhs went into this vismaad anand state, as the taste of the parshade was of nothing they had ever tasted before. then the singhs asked sant gurbachan singh ji as to why they went into that vismaad state, and sant ji explained that baba ji is a pooran brahmgiani, and that anything they touch, they turn into pavitar, no matter if they wash their hands or not.
this one other time, i think giani ji went with sant kartar singh ji, or maybe sant jarnail singh ji, to meet baba ajit singh ji. and the singhs of the jatha asked baba ji, to give the definition of a gurmukh and a manmukh. and these are the bachans of a pooran brahmgiani:
"bhai jis de mukh vich hamesha guru guru eh, oh gurmukh, tey jis de mukh vich kush hor, oh manmukh".
nice and simple.
meaning that whoever is always doing simran, and has waheguru on their tongue, thats a gurmukh, and whoever has something else on their tongue, thats a manmukh.
alot of times, people would go to meet baba ji, and they would be walking in the fields while people would come up to them and ask them "we wanted mahapurshan de darshan, do you know where we can meet them" and such nimarta of baba, they would always answers back, "pata nahi bhai, ehthey kithe hunne ne" meaning, "idk he must be here somewhere" baba ji would act like he is not a mahapursh. then after waiting for some time, the people would ask the sevadaars about where baba ji is, and the sevadaars would tell them that the person who they saw walking in the fields, who they first talked to, that is baba ji himself.
and i dont think they have a biography, but if u go to punjab, u can ask around tho.
