Is it obligatory to share the electricity bill amount with a brother, taking into account that social security pays a portion of it because he is covered by social security, or to give him what social security paid from my share, or to give it as charity?

If the warranty provides a fixed amount regardless of usage, then there is no harm in subscribing to the meter and sharing the bill. However, if the warranty provides a percentage based on consumption, then he must be informed of the reality of the subscription or the need for a separate meter, so that it does not become consuming wealth unjustly.