Will I get notified if any other owner give owner access to some other accounts in GCP?

You won't be notified the any of the project owners added another one. But there's a workaround.

You can view such actions in the logs explorer by selecting a resource projects/your_project_Name/logs/cloudaudit.googleapis.com%2Factivity;

See the Cloud Audit Logs documentation for more info.

Then you can create a custom metric for that and create alerting policy based on it that will be sending predefined message to an email, pub/sub or a bucket.

You can also create a sink for such logs and store them in a bucket or BigQuery.

That way you can keep track of any changes in IAM permissions and get notifications whenever any other owner get added (or removed).

By default not. But you can build something to be notified. Actually, when you perform admin actions, these actions are logged in the audit logs.

You can filter these logs with Cloud Logging and sink them in PubSub.

Then you can consume PubSub message and send notifications.

In addition, with SCC (Security Command Center) you can also have realtime notification when primitive role (i.e. owner, editor, viewer) are granted on a service account. Here again, a notification is a PubSub message and consume it as you need.

You can have a look to the documentation