Complex sentence: In 1903, he married another Siberian transplant to the capital, Sofiya Vasilievna Kokoulina, one of six children born to a Russian Siberian native.
Split into simpler sentences: In 1903, he married Sofiya Vasilievna Kokoulina, another Siberian transplant to the capital. Sofiya herself was one of six children born to Vasiliy Yakovlevich Kokoulin, a Russian Siberian native.