Dear Andrij,
Just a few corrections. The father of Ostap Nizhankovsky was Iosyf Nizhankovsky (1836 - 06.03.1911), not Osyp. Ostap had a sister - Olena, who married the Ukrainian Cathoic priest Nykolai (Mykola) Yarosevych. They had five chilren, the fourth of which was Irena Yarosevych , who became a Polish star under the name of Renata Bogdanska.
Best,
Bohdan Nahajlo