Absolutely. There were tons of these kinds of efforts. I know more about what happened to children, so I'll start there.

Children were a tricky issue. Former slave owners didn't want to give up control of the newly freed children for a few reasons. They wanted the kids' labor and/or they wanted to keep the parents working on their farms/plantations, so they kept the kids to make sure that the parents stayed close. At any rate, most states in the US had laws on the books that allowed the courts to apprentice children. It was a way of dealing with poor and orphaned children, both black and white. Think of it kind of like foster care (though there were some key differences). A kid who didn't have parents or whose parent's were too poor to care for the child would be placed in a new family. An apprenticeship granted the adult legal custody of the child until he or she became an adult (age 18 for girls and 21 for boys). Again, this happened all the time for both black and white children.

After emancipation, slave owners that wanted to keep control over formerly enslaved children flocked to courts to have the children apprenticed. Now, often the laws governing these apprenticeships required the parents to consent to the arrangement (you will also see these arrangements called indentures). For black men and women during Reconstruction who were dealing with racist white judges, showing up in a courtroom was consent (even if they said the words, I do not consent, they were ignored and the judges apprenticed their children). Not showing up in court was understood as consenting to the apprenticeship by default. This is what often happened to children who were freed, but had been separated from their parents. The white former slave owners claimed that the children did not have anyone to provide for them, so their former owners gained legal custody through an apprenticeship.

In many states, the Freedmen's Bureau agents fought against this kind of apprenticeship and had them overturned and the children returned to their biological parents. Usually, the parents would file a complaint with the Freedmen's Bureau about the children being held illegally and Bureau agents would confront the master and force him or her to return the children. The parents generally knew where the children were and who held them, so the Bureau agents went on this information. Basically, a federal agent would write letters or even visit the white former slave owner, ask about the kids, and demand their release. For children who were really orphaned, with no parents or relatives to take them, Bureau agents would actually take the children to the courts and have them apprenticed to someone who would keep the child until he or she became an adult.

I'm less knowledgeable about how adult family members were reunited. Here's what I do know. One of the goals of the Freedmen's Bureau was to help freedmen and women create families that at least looked similar to the white middle-class families in the North with a male breadwinner, a mother, and children. In some instances, they wrote letters or paid the transportation costs for family members to travel and reunite with their families. Slaves could not be legally married. Under slavery, they set-up "marriages" where slaves would be coupled off, but there was no legal recognition of the relationship. After emancipation, the Freemen's Bureau encouraged men and women to get legally married (Bureau agents kept registers of the marriages between freedmen and women--these are often online or in the national archives). In addition to the Freedmen's Bureau, there were a lot of private philanthropic organizations that were working to encourage the reunification of slave families. Though, it's worth noting that the freedmen and women did a lot of this on their own. There are tons of newspaper ads where former slaves were seeking information about their family's whereabouts. Sometimes they were successful, other times, not so much.

I'm relying on a ton of different sources for this stuff. For primary sources, you can look at a website called [The Freedmen's Bureau Online] (http://freedmensbureau.com/). The documents are organized by states. Most of the states have marriage registers you can look at and North Carolina has an order from the Freedmen's Bureau canceling the indentures or apprenticeships made for black children. It's a really cool website that is worth checking out. To get a sense of what Freedmen's Bureau agents wanted black families to look like after emancipation, I would recommend the short pamphlet by Clinton B. Fisk, Plain Counsels for Freedmen. You should be able to turn up a copy with a quick google search. It was written in the 1860s, so it's in the public domain. It's short and super interesting.

For secondary sources, Eric Foner's book titled Reconstruction: America's Unfinished Revolution, 1863-1877 has a lot of this material (there is a gigantic version and an abridged version--I've only read the long one, but the abridged version should get you this information too). If you are interested in issues related to marriage after emancipation, I would suggest Nancy Cott's book Public Vows. Her book covers the colonial era through the 2000s, but she has a chapter or two on Reconstruction (the entire book is pretty fantastic for showing why local, state, and federal governments care so much about marriage).

Edit: deleted a duplicate paragraph after a copy and paste fail.