Erich also received messages of love and support from The Bachelorette host Jesse Palmer, fellow Season 19 bachelors James "Meatball" Clarke and Logan Palmer, and many other members of Bachelor Nation.
Allan's cancer battle began with appendiceal cancer, a type of cancer that grows from cells that make up the appendix. Allan was once in remission, but his cancer returned aggressively and then he endured three intensive rounds of chemotherapy, the last of which "almost killed" him, according to Erich's father on The Bachelorette's latest episode.
Allan had spent 40 days in the ICU following multiple operations before Erich's hometown date with Gabby in New Jersey filmed.
"That was the first time that I, like, really cried from all that. It's been a journey," Erich continued to share with Gabby.
"The only thing that's really [kept] me going is how loyal my mom was to that relationship and to him. At no point was she giving up. It's a bond that they have that I think it's really rare to come by. I need you to meet them. And I need them to meet you in order to move forward with this."
Erich later said in a confessional of Gabby, "I know she's the one that I want to bring home. I know she's the one that I want to be here. I'm excited for her to meet my family and especially my dad... I have to show my dad how much she means to me."
Allan "really liked" Gabby once he got to know her, and Erich pointed out how that was a "huge sign" for him that he was heading in the right direction on the show.
Gabby, being an ICU nurse, could also relate to Donna's hardships given Donna had been taking care of her husband at home for years, which Donna dubbed "a labor of love."
When Gabby and Donna got a chance to speak alone, Erich's mother gushed about Allan.
"We all love him. You can't not love Allan. He's a great guy. So, I just want to make sure that you guys -- if you decide anything -- [know] that commitment in my family is really important," Donna told the Bachelorette with tears in her eyes.
"We don't give up on each other. You can't quit -- ever [or] for anything. We'll be married 35 years, and we've been through a lot. You always have to stay together and be together, always."
Gabby assured Donna that she cared for Erich a lot, and the Bachelorette thought Erich's date was extremely special.
"I felt so close to them," Gabby revealed. "Today with Erich was one of the best days I've had so far. Seeing him with his family really made my feelings so much deeper for him."
That night, Erich told Gabby that he was "falling" -- and "maybe" even "falling in love" -- with her, and Gabby opened up about how she reciprocated those feelings.
"I think I've always wanted to be with someone like you but just never knew if it was possible. But after today, I do finally feel comfortable in saying that I am falling in love with you," Gabby told the suitor.
Gabby concluded that she'd never forget Erich's hometown and that date may have changed the rest of her life.