A dear friend’s son was raised with 3 languages in the home; English, Czech, and Spanish. When he was a toddler he asked me a 3 word sentence with one word from each language and looked at me like I was an idiot for not knowing them. I will say it was struggle for his mom to try to keep him speaking all 3 languages once he hit school age. He was educated in England and English just became his default. He maintained some Spanish by spending summers in Spain. But she gave up on him speaking much Czech. I know she’s speaking Czech almost exclusively to her youngest. I’ll have to ask if that’s getting her oldest to speak Czech again.