There is no mention of his parents or siblings in his obituary. Here's my transcription:
Tampa Morning Tribune
Monday - 12 March 1928
Page 2 - Column 4
Deaths and Funerals
M. L. Nance
M. L. Nance 77, died at his home, 1515 Nance avenue, yesterday morning at 7 o'clock after an illness of a year or more. He is survived by his wife; a son, Dr. C. L. Nance, of Tampa, and two daughters, Mrs. D. F. Owen, of Tampa, and Mrs. G. F. Grant, of Abingdon, Va. Funeral services will be held from the residence this morning at 10 o'clock, conducted by Dr. J. C. Tims, of the Presbyterian church, and Dr. T. W. Raymond. Pallbearers will be J. F. Alexander, H. C. Giddens, Sr., W. L. Pearson, C. J. Courath, J. R. Curry and D. H. Sumner.
There was another news article from 18 Decemeber 1924 regarding the Golden Wedding Anniversary celebration for Marcus & Lina that was hosted by their children. It is far too large to transcribe but it does state the following:
"Mr. and Mrs. Nance were married fifty years ago in Ripley, Miss., and have resided in Tampa for the past five years, where they are beloved by a wide circle fo friends."
This ties Marcus to Ripley, MS where you will find several years of US census records tracking back to his childhood.
Here's a link to the Death Notices of Tippah County: http://www.rootsweb.ancestry.com/~mstippah/DeathMNO.html
The entry for M. L. Nance states his brother was Ruff Nance. There are several other entires for Nance family members but you'll need to read thru them to find more siblings that you can tie to your Marcus. By researching the siblings you may be able to confirm parentage for all.
Happy hunting -