It is not sure, if Seti II. was a son of Merenptah and queen Isetnofret or according to E.F.Wente and J.R.Harris didn't came from the dynasty. If we admit that Amenmese was a power usurper, he might ruled in Lower Egypt at certain time of Seti II. We know for sure that Seti II. ordered to remove the decorations from the grave of Amenmesse in the Valley of the Kings.
As well as his predecessors Seti II. continued in building in Karnak, where he let build among others a chapel of Theban triad – Amun, Mut and Khonsu.
Seti II. was buried in tomb KV 15 in the Valley of the Kings. His mummy was likely transfered to the tomb of Twosret KV 14 in the last year of he reign and later the mummy was returned into the first tomb. Finally the mummy was found in a hideaway of Amenhotep II. tomb – KV 35.
Replica of a relief of Seti II holding a shrine to the god Amun on display
at the Rosicrucian Egyptian Museum in San Jose, California.