'I would say it's Ioann.'
I wonder whether it's actually one of KR's younger children. KR was born in 1858 and so was 28 when Ioann was born in 1886. Even making allowances for beards and crew cuts tending to make a man look older, he looks older than that (is there grey in his hair - impossible to tell with a black and white picture, however).
Ann