Seems like it was worth waiting so long for the responses to come giraffe90 :D

'Jaan' general mean 'life' and it use in different ways in different contexts.

In Pakistani punjabi culture 'Jaan' used between lovers. (Meri jaan kesi ho?) Its like saying 'My Baby'.

informally used between male friends (Meri jaan ke totay) to show close relationsip or for tauning an enemy in funny way.

And there is no way that a married female can use 'Jaan' for cousin. She can only use for husband, dughter and son.

Jaan is similar to Ji in Punjabi and Hindi languages.. It is to show respect:  Like Bhai Jaan is used for brother, cousin, for brother In law.  Ammi Jaan,  for mother,  , taau jaan, Tayi Jaan, for dad's elder brother and his wife respectively,   chcha jaan, chachi jaan for dad's younger brother and his wife.  bhabi jaan.  for brother's wife.

it is just to be respectful, I think.

Definitely, it is not for lover. In that sense, Jaan means, omg I could not think of the word in English, jaan means feeling of being alive.  when people in love call  each other jaan,  it means that he or she is that important. In Hindi and Punjabi languages people use jaan word in this sence, mean for lover but for Urdu Jaan could be used for any relation to be respectful.

Jaan is also used for these relations when addressing them with respect.

Brother: bhai jaan

Father: Abba (abbu) jaan

Mother: Amman (ammi) jaan

Grandmother:  nani jaan (mother's mother), dadi jaan (father's mother)

Grandfather: Nana jaan (mother's father), dada jaan (father's father)

Uncle: chacha jaan, taya jaan (father's elder brother).

Aunt: chachi jaan

etc.