You can link a citation of a source to more than one fact via two methods:
1) Copy one citation and paste-link or paste-duplicate to one fact at a time; or:
2) Cite a source to a fact and then copy that fact to all of the persons of that immediate family and his parent's immediate family in one operation.
For number one above:
1) Select a fact to link the first citation to.
2) Make the (first) citation to that fact via the New button
3) Then, select that citation and either right-click copy or copy via the button bar icon (2 pieces of overlapping paper under the itty-bitty down arrow next to New).
4) Then, move to another fact for that person or any person anywhere in your file, place your mouse in the citation area for the fact and choose either right click paste-duplicate or right click-link, or just choose one of those two options from the button bar - the itty-bitty little down arrow next to New.
PASTE-DUPLICATE is if you are going to change something about the citation that will be unique and different from what you originally copied; for example a page number from a book.
PASTE-LINK is if you are want to paste an exact clone of a citation that is identical to the first citation to the second fact. For example, if the page number of the source is the same number.
Number Two - Same Fact for Multiple People
Create a Fact for a person.
Make your citation to the Fact
Select the Fact again.
Right click - Copy the Fact (which includes all citations)
If you are wanting to paste the fact to other people in this person's immediate family, then right-click again, but choose Paste.
This will bring up a screen showing parents, siblings, childre, and spouses of that person with checkboxes next to each and "ALL" at the top.
Then click ok
That single fact from one person, with associated citations, will copy to all people you choose on that page.
You can then move to other people, or family groups in your file to copy that fact to. This Since you are copying to parents and siblings and children, it is actually copying to two families at once: the selected person's family and his parent's family.