Find Ancestors

I am trying to find out what happened to my grandmother's elder siblings. Their parents were Richard Charles Evans (b. approx. 1838 in Cardiganshire - probably Llanrhystyd) and Margaret Morgan (b. 1835 in Rhayder). They were married in 1859 in Rhayader and then seemed to move around a bit. In the 1861 Census, they were living in Llangeitho with baby daughter Margaret Ann. In 1871 they were in Ebbw Vale, with four other children, Richard (b. 1862 approx.), Mary b. 1866 approx., George (b. 1868 approx.) and David Charles (b. 1870). It appears Margaret was living or staying with her aunt and uncle (sister and brother), Mary Anne Jones and John Morgan, in Rhayader at that time. In 1881 they were living in Llandaf and my grandmother, Ellen Blanche, b. 1876, had been added to the family. Once again Margaret was listed in Rhayader with her grandmother, Margaret Morgan, this time. In the 1891 Census, only David and Ellen were still living with their parents in Cardiff. I did find a younger Richard Evans who might have been her brother living in Cardiff, with a wife Harriet and two young children, Richard and Margaret (I figured that sounded like the right famiy!) However, this is not certain and I couldn't find them in the 1901 Census. Margaret and Mary I couldn't find at all. George was living with his wife Amy (Bromwell) in Cardiff. The elder Richard died in 1892 and some time after that my great-grandmother and grandmother moved back to Rhayader, where they were living in 1901. I could find George and Amy, with 3 daughters, Dorothy, Violet and Haulwen Elfreda, in Cardiff, but none of the other siblings. I do know from one of his descendants that David Charles had married Harriet Louisa Rodda and by then they had a few children. My grandmother married in late 1905 to a Scot, George Smith, who was working in Wales, and they left for Canada the following year, however, making a visit back in 1908 when my mother was born in Cardiff. She also made a trip back in the summer of 1925 and I have an autograph book of my mother's where a number of her cousins, aunts and uncles signed. I can trace George's descendants to his daughters and have been able to go to the present day with one of David's descendants, but would like to find out more about Richard, Margaret and Mary. If any of this sounds familiar to anyone, I'd love to hear from you!