In genealogy and wills, issue refers to a person's lineal descendants.
Lineal Descendants
"Issue" typically means a person's lineal descendants—all genetic descendants of a person, regardless of degree. Issue is a narrower category than heirs, which includes spouses, ancestors, and collaterals (siblings, cousins, aunts, and uncles). This meaning of issue arises most often in wills and trusts.
References
Issue (genealogy) Wikipedia(Text) CC BY-SA