I forbid my children from playing on the phone but I am always on mine. Does this undermine their upbringing?

Children learn from what they see, not what they hear, so the phone in your hand teaches more strongly than your ban. Allah rebukes double standards: “why do you say that which you do not do?” (Surah as-Saff 61:2). Start with yourself: put the phone down at certain times such as meals and before bed, and give your children your full attention. Announce the same rules for everyone, including you, so that they feel fair. When children see you reading, playing or chatting without a screen, they copy you. A consistent example is more effective than a thousand warnings. See the family's digital life.