If you have no idea what year someone was born or died but you want to show the person as a parent or partner or child in a person-article, please add " (-)" after the name.
One big advantage is that such a name should never be a redirect to an individual's article and therefore never create a false relationship.
Earlier today I created Gilbert Kennedy (c1368-c1440)/descendants without having studied Gilbert's base article, a rather ancient page, and was shocked to see that one of his sons was John Fitzgerald Kennedy (1917-1963). I refreshed the sensor page then opened Gilbert's edit box and looked at his children's code lines; I saw no explanation until I saw his son "John Kennedy" and realised that John Kennedy now redirects to that world-famous 20th-century politician.
Tree subpages and main articles will all be liable to create such false links, so please don't leave bare names attached to them.