Qrow's age maybe look like 30s? Since his nieces were born, one is born from Raven, and other born from Summer. He maybe old, but he not yet to be like age. Well, since he can still fight during the fight against Winter.
Well, assuming Raven had Yang just after she graduated from Beacon at 21/22 years old and all members of STRQ are the same age, then Qrow would logically be 38/39 years old. This is probably the youngest the previous generation can be, as there has been no mention of anyone dropping out of Beacon to raise a child.