Some people are surprised to know that some Gurus had multiple wives. However for some reason, this multiple wives theory is only for Gurus who lived like Kings, 6th, 7th and 10th Guru. Only 10th Guru had 2 wives. These Gurus never had an expanding kingdom but autonomous cities, so marrying for political reasons is out of the window. They were also beyond lust as 10th Guru refused to have any physical relations with his future second wife.Most of these stories are written in books which also contains teachings which are completely opposite of SGGS. It is possible that they remarried after the death of previous wife as in the case of 5th Guru. Bhai Gurdas mentions the difference between Guru Hargobind and previous Gurus in his Var 26 pauri 24 but does not mention multiple wives, but mentions that a Sikh should have only one wife in his Var 6 pauri 8. Guru Granth Sahib also mentions one partner on Page 788.