A few years after he graduated

[Bassim]

I am wondering if my sentences are grammatically correct.

A few years after he graduated from university, Tony lost contact with all his former fellow students. He reminisced with irony about how they used to promise a lifelong friendship to each others and regular meetings, which never took place.

 

[Tdol]

It's OK as long as you change each others to each other.

 

[GoesStation]

Try starting with Tony.

They'd be more likely to promise each other lifelong friendship in natural English.

Regular meetings is unnatural. They might promise to get together regularly.

 

[Bassim]

I will repeat my sentence.

Tony lost contact with all his fellow students a few years after he graduated. He reminisced with irony about how they used to promise each other lifelong friendship and get together regularly, which never took place.

 

[GoesStation]

Try this:

Tony lost contact with all his fellow students/classmates a few years after he graduated. He remembered - not without a tinge of bitterness - how they had all promised to be friends for life. They were going to get together regularly, but it never happened.

"Reminisced with irony" doesn't work at all.