Sentence:  While some adoptive parents may tend to try and shy away of such discussions with their adopted children, it is very important for them to understand that a desire to connect to that <WSD>thread of life</WSD> that nonadoptees are granted is a natural instinct -- and should not be viewed as a threat to their family. 
Meaning of the word marked with <WSD> tags:  The link of inheritance from past to present.