The names transcribed are: Ivan Mikhaylovich Sen'kov and Yevdokiya Kondrat'yevna Sen'kova.
There is no information on the old man in the photograph, but if he happens to be be Ivan's father, He name would be Mikhail Sen'kov.
The poem at the bottom of Yevdokiya's plaque says:
Дорогая мама, спи в земле сырой,
мы пришли к твоей могиле
с горем и тоской.
[= Dear mama, sleep in the damp earth,
we have come to your grave,
with grief and sorrow.
The dates on Ivan's headstone are almost illegible. Best guess is recorded.