Can a field reference to 2 different FKs or any better option for this case?
CREATE TABLE `settings` (
  `setting_id` int(6) NOT NULL,
  `description` varchar(32) NOT NULL,
  `code` int(6) DEFAULT NULL,
  `created` datetime NOT NULL,
  `updated` timestamp DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
  PRIMARY KEY (`setting_id`),
  KEY `code` (`code`),
  CONSTRAINT `settings_ibfk_1` FOREIGN KEY (`code`) REFERENCES `field_values` (`fv_id`) ON UPDATE CASCADE
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

create table Setting (
      SettingID   integer     not null
    , SettingType char(1)     not null
    , SettingName varchar(32) not null
    , Description varchar(32) not null
    , Created     timestamp default CURRENT_TIMESTAMP
    -- other common-to-all-setups columns here
);
alter table Setting add constraint pk_setting primary key (SettingID);


create table LanguageSetting (
      SettingID   integer     not null
    , Updated     timestamp default CURRENT_TIMESTAMP on update CURRENT_TIMESTAMP
    -- other columns specific to this setup-type here
);
alter table LanguageSetting
  add constraint pk_langset  primary key (SettingID)
, add constraint fk1_langset foreign key (SettingID) references Setting(SettingID);


create table AgeFilterSetting (
      SettingID   integer     not null
    , Updated     timestamp default CURRENT_TIMESTAMP on update CURRENT_TIMESTAMP
    -- other columns specific to this setup-type here
);
alter table  AgeFilterSetting
  add constraint pk_ageflt  primary key (SettingID)
, add constraint fk1_ageflt foreign key (SettingID) references Setting(SettingID);


create table OtherSetting (
      SettingID   integer     not null
    , Updated     timestamp default CURRENT_TIMESTAMP on update CURRENT_TIMESTAMP
    -- other columns specific to this setup-type here
);
alter table  OtherSetting
  add constraint pk_othset  primary key (SettingID)
, add constraint fk1_othset foreign key (SettingID) references Setting(SettingID);

CREATE TABLE [Child1](
    [ParentId]  int    NOT NULL,
    CONSTRAINT [PK2] PRIMARY KEY CLUSTERED ([ParentId])
)

CREATE TABLE [Child2](
    [ParentId]  int    NOT NULL,
    CONSTRAINT [PK3] PRIMARY KEY CLUSTERED ([ParentId])
)

CREATE TABLE [Parent](
    [ParentId]  int    NOT NULL,
    CONSTRAINT [PK1] PRIMARY KEY CLUSTERED ([ParentId])
)


ALTER TABLE [Child1] ADD CONSTRAINT [RefParent1]
    FOREIGN KEY ([ParentId])
    REFERENCES [Parent]([ParentId])

ALTER TABLE [Child2] ADD CONSTRAINT [RefParent3]
    FOREIGN KEY ([ParentId])
    REFERENCES [Parent]([ParentId])