Looking for Birth Siblings-Louisiana-mid to late 1950's

I was adopted at birth. My original birth certificate listed mother as Bettye Knight. My birthday is 4/21/1958. In 1999, I was reunited with a birth sister and brother that were raised by the birth parents and a birth sister that was given up for adoption at birth as well. The birth parents are now deceased. Their names were Frances Elizabeth "Bettye" Knight and Egbert "Red" Morris. All of us have discovered there were more siblings, at least two born to this mother and we are trying to locate them. The first one was born before the birth mother was married. The child was born in the Methodist Home in New Orleans. The exact year is unknown, but estimated to be between 1954-1956. The 2nd child was born at the Cedar Grove Clinic in Cedar Grove Louisiana, a suburb of Shreveport. The year is 1959. This clinic has been closed many years now and we haven't been able to locate the records. The birth parents may or may not have been listed as the parents on this original birth certificate, they were still not married at this time. My sister that was given up for adoption as well found her original birth certificate and the mother's name was as I stated mine was above, but on both the father's name was not listed. He was married to another person at the time of our births. My youngest brother born in 1962 is the only sibling born after they married. We don't want anything from these siblings other than to let them know they have other brothers and sisters that would like to get to know them. Since our reunion, we have started traditions at Thanksgiving and Christmas and get together as often as we can. It will be 4 years this coming July since we reunited and have grown to love and care for each other deeply. I hope we can eventually find the still missing two other siblings as well.