Michael Lynam, son of Michael and Mary/Maria Smart

This is the only one 1849-51Dublin from www.rootsireland.ie/:

Name:Michael LynamDate of Birth:
Date of Baptism:28-Jan-1850Address:Not RecordedParish/District:ST.PAUL'S ARRAN QUAYGender:MaleCountyCo. Dublin
Denomination:Roman Catholic
Father:James LynamMother:Mary LynchOccupation:
Sponsor 1 /
Informant 1:Catherine Charles 

I couldn't find a marriage record of the parents in any year or county

This is the only sibling from roots:

Name:Mathew LynamDate of Birth:
Date of Baptism:17-Jan-1853Address:
Parish/District:ST.PAUL'S ARRAN QUAYGender:MaleCountyCo. Dublin
Denomination:Roman Catholic
Father:James LynamMother:Mary LynchOccupation:
Sponsor 1 /
Informant 1:Mary Byrne 

www.irishgenealogy.ie/ is good for Dublin records in case you haven't tried there.

Col

jwkerry:

I looked at the subscription site Roots Ireland as Col suggested and found four baptismal records for children of Michael and Maria/Mary Smart. The first two were in Donabate parish and the last two in Balbriggan so obviously they moved north at some point. Catherine 1844 Mary 1845 Patrick 1860 Elizabeth 1864

There is a 15 year gap between Mary and Patrick so in addition to Michael there were likely other children. I also scanned the Donabate parish register from 1847-1852 with no success.The Balbriggan register has a index to their register and the only baptisms for children of Michael Lynam and Maria Smart were the forementioned Patrick and Elizabeth. There are no records in Dublin city parishes.

Any possiblility they went to England or Scotland between 1845-1860? 

Roger McDonnell