Simplify the following text for a Grade 10 native English-speaking person.
Original: Some historians believe Rommel also had a relationship with Walburga Stemmer in 1913 , which allegedly produced a daughter , Gertrud .
Simplified: After having met Lucie , some historians think that Rommel also had an affair with a woman called Walburga Stemmer in 1913 , and they had a daughter named Gertrud .