Using this code:   data both; set schoolsurvey sixthgraders; run; proc print data=both; title 'Data Set Appended'; run;   I got this output: Data Set Appended  Obs Family_id Student_ID School Grade DOB12345 90021 103699   4th 07/24/2004 90021 127945 RG 6th 01/26/2002 90021 149229   2nd 10/28/2005 90053 109831 RC 6th 08/27/2002 90053 122779   5th 08/28/2003   Using this code: data combined; merge schoolsurvey sixthgraders; by Family_id; run; proc print data=combined; title 'Data Set Merged'; run;   I got this output: Data Set Merged  Obs Family_id Student_ID School Grade DOB12345 90021 127945 RG 6th 01/26/2002 90021 127945 RG 6th 01/26/2002 90021 149229   2nd 10/28/2005 90053 109831 RC 6th 08/27/2002 90053 122779   5th 08/28/2003   I'm confused, as merging the data replaces the 4th grade sibling with the family_id of 90021 with a duplicate of the 6th grade sibling.   I do not think we are accounting for twins, triplets, skipped grades, etc. I believe it is as simple as seeing if the family_ID is the same in the combined data set for obs 1 and 2 and taking the difference between year(DOB) for observation 1 vs observation 2, and then looping that. I just don't know how to put that into SAS logic, and was hoping someone could provide me with a bare-bones example of how I would go about approaching this.   I'm uncertain as to what you mean by renaming the variables before the merge, as well.   Thank you, and sorry for my misunderstandings. ... View more

Thank you for the reply! The siblings are indicated by family_id--if they share the same family id, then they are siblings, and yes, sometimes there are more than one sibling to a sixth grader.   I'm not particularly apt at creating examples The data is simply imported from the file schoolsurvey.sas7bdat; not data that I created or obtained on my own   it has the variables family_id, student_id, school, grade, and DOB for example, observation one has these values (for each variable respectively, and I am separating them with commas for this post so they are easier to read): 90021, 103699, (the school is blank), 4th, 07/24/2004 ... View more