Get value of another field in Field level Validation in DRF

No that is not possible. If you need to access more than one value you have to use the Object-level validation (see docs):

class Keys_Serializer(serializers.Serializer):

    key_id = serializers.IntegerField(required=True)
    key_name = serializers.CharField(required=True)
    value_id = serializers.IntegerField(required=False)

    def validate(self, data):
        # here you can access all values
        key_id = data['key_id']
        value_id = data['value_id']
        # perform you validation
        if key_id != value_id:
            raise serializers.ValidationError("key_id must be equal to value_id")
        return data